Studies on the fresh properties an durability of unshrinkable fill containing recycled concrete aggregate or natural aggregates of marginal quality

Sulphate Attack ◽

Fresh Properties ◽

Severe Damage ◽

Sulphate Content ◽

The intention of this research is to explore the feasibility of incorporating aggregates of low or marginal quality, such as Recycled Concrete Aggregate (RCA) and aggregate with high sulphate content, in U-fill mixtures. It has been determined that where RCA is used, water dissipation may be hindered due to the increase in fines caused by abrasion, hence causing an increase in hardening time. To reduce this effect, addition of natural aggregates may be necessary. Moreover, through a series of investigation it has been found that high percentages of sulphate may cause severe damage due to Ettringite and Thaumasite formation; however by incorporation of supplementary materials such as slag the deleterious effects of internal sulphate attack can be reduced. The effects of using Na2SO4 and gypsum in the presence of slag have also been investigated. Results indicated that due to the lower available calcium content within bars containing Na2SO4 expansion rate is low.

Physical, Deformation, and Stiffness Properties of Recycled Concrete Aggregate

Sustainability ◽

10.3390/su13084245 ◽

2021 ◽

Vol 13 (8) ◽

pp. 4245

Author(s):

Katarzyna Gabryś ◽

Emil Soból ◽

Wojciech Sas

Keyword(s):

Recycled Concrete ◽

Experimental Program ◽

Concrete Aggregate ◽

Test Results ◽

Granulometric Analysis ◽

Stiffness Properties ◽

Grain Distribution ◽

Natural Aggregates ◽

Critical Reduction

The construction sector is currently struggling with the reuse of waste originating from the demolition and modernization of buildings and roads. Furthermore, old buildings are gradually being replaced by new structures. This brings a significant increase of concrete debris to waste landfills. To prevent this, many studies on the possibilities of recycling concrete, known as recycled concrete aggregate (RCA), have been done. To broaden the applicability of reused concrete, an understanding of its properties and engineering behavior is required. A difficulty in sustainable, proper management of RCA is the shortage of appropriate test results necessary to assess its utility. For this reason, in the present study, the physical, deformation, and stiffness properties of RCA with gravely grain distribution were analyzed carefully in the geotechnical laboratory. To examine the mentioned properties, an extensive experimental program was planned, which included the following studies: granulometric analysis, Proctor and oedometer tests, as well as resonant column tests. The obtained research results show that RCA has lower values of deformation and stiffness parameters than natural aggregates. However, after applying in oedometer apparatus repetitive cycles of loading/unloading/reloading, some significant improvement in the values of the parameters studied was noticed, most likely due to susceptibility to static compaction. Moreover, some critical reduction in the range of linear response of RCA to dynamic loading was observed.

Adhesion between Asphalt and Recycled Concrete Aggregate and Its Impact on the Properties of Asphalt Mixture

Materials ◽

10.3390/ma11122528 ◽

2018 ◽

Vol 11 (12) ◽

pp. 2528 ◽

Cited By ~ 10

Author(s):

Yueqin Hou ◽

Xiaoping Ji ◽

Jia Li ◽

Xianghang Li

Keyword(s):

Free Energy ◽

Surface Energy ◽

Asphalt Mixture ◽

Recycled Concrete ◽

Fatigue Performance ◽

Concrete Aggregate ◽

Water Stability ◽

Adhesive Energy ◽

To study and evaluate the adhesion between recycled concrete aggregate and asphalt, the contact angles (CAs) between droplet (water and ethanol) and recycled concrete aggregate (RCA), natural aggregates, and solid bitumen (matrix asphalt, SBS modified asphalt) were tested via the sessile drop method with an optical microscope. The surface free energy was then calculated. The CAs between hot asphalt and RCA and natural aggregates were tested via the hanging slice method. The adhesive energy between asphalt and RCA and natural aggregates were calculated based on the test results of the surface free energy and CAs. Then, the influence of RCA on the water stability and fatigue performance of the asphalt mixture was analyzed by testing the water stability and fatigue properties of hot mix asphalts containing RCA (HMA-RCA) with different aggregates and RCA dosages. The surface energy of the various aggregates and the CAs between aggregates and asphalts were sorted as follows: Granite > RCA > serpentinite > limestone. The surface energy and CA of RCA were very close to that of serpentinite. The adhesive energy between various aggregates and asphalt were sorted as follows: Limestone > serpentinite > RCA > granite. The adhesive energy between RCA and asphalt was also very close to that of serpentinite. The residual Marshall stability, tensile strength ratio, and fatigue performance of the HMA-RCAs were gradually reduced along with the increasing RCA dosage. This effect may be attributed to the fact that the adhesive energy between the RCA and the asphalt was less than that of water and that the asphalt was easily stripped from the RCA surface. Excessive RCA content in the aggregate can lead to excessive porosity of the HMA-RCA. The CAs and adhesive energy between RCA and asphalt showed significant effects on the water stability and fatigue performance of HMA-RCA.

The use of lithium salts and supplementary cementing materials to control reactivity of recycled concrete aggregate

10.32920/ryerson.14663910.v1 ◽

2021 ◽

Author(s):

Waleed Mikhaiel

Keyword(s):

Preventive Measure ◽

Calcium Content ◽

Recycled Concrete ◽

Alkali Silica Reaction ◽

Alkaline Solutions ◽

Concrete Aggregate ◽

Second Phase ◽

Lithium Nitrate ◽

Supplementary Cementing Materials

This thesis covered the second phase of a study that focused on the reactivity of recycled concrete aggregate (RCA) produced from concrete affected by alkali-silica reaction (ASR). The first phase investigated the reactivity of ASR-affected RCA and the use of Supplementary Cementing Materials (SCM) as a preventive measure. The second phase was carried out to study the efficacy of lithium nitrate, when used individually and in combination with SCM, in suppressing the reactivity of RCA. The use of different dosages of lithium nitrate combined with SCMs reduced expansion due to ASR. However, the expansion results showed that increasing the dosage of lithium beyond a certain level does not help in suppressing the expansion. The high reacitivity of the tested RCA was attiributable to its relatively high alkalis and calcium hydroxide contents that fuel further ASR. The alkalis consumed or contributed from RCA were evaluated through leaching the aggregate particles in distilled water and alkaline solutions at different molarities with and without lithium nitrate. Alkalis consumption was found to decrease when lithium was presented in the leaching solutions. Examining RCA samples under scanning electron microscope (SEM) showed that the crushing process of the RCA exposes fresh surfaces of the reactive virgin aggregate and creates cracks within the particles that provide an easy path of alkalis to reactive sites within the RCA. Examination of the composition of ASR gel showed that exposing the RCA to lithium solution decreased the calcium content and Ca/Si of the gel. This could add to the suggested mechanisms by which the lithium mitigates ASR.

Performance of Self Compacting Concrete Incorporating Coarse Recycled Concrete Aggregates Exposed to Sulphate Attack

International Journal of Recent Technology and Engineering - 2 ◽

10.35940/ijrte.e6854.018520 ◽

2020 ◽

Vol 8 (5) ◽

pp. 4797-4806

Keyword(s):

Sodium Sulphate ◽

Recycled Concrete ◽

Sulphate Solution ◽

Strength Development ◽

Natural Material ◽

Concrete Aggregate ◽

Coarse Recycled Concrete Aggregate

Sulphate Attack ◽

Self Compacting Concrete ◽

The interpretation of the performance of self-compacting concrete made with distinct proportion of coarse recycled concrete aggregate (RCA) (0%, 25%, 50%, 75% and 100%) exposed to sodium sulphate solution (50 gram/litre) under fully immersion condition is studied in this paper. Compressive and tensile strength development/degradation, mass change and length change under sulphate attack was surveyed for all tested units. According to the results it can be conclude that the use of coarse recycled concrete aggregate does not affect the development of strength of concrete with respect to natural material mixtures. It also conclude that for producing of sustainable and green concrete, the quality of used coarse recycled concrete aggregate is an important factor. The differ proportion of coarse recycled concrete aggregate & duration of immersion of concrete in sulphate solution also affect the concrete properties. Reusing recycled combination has twin property benefits: benefiting many tons dismantled concrete worldwide and conserving natural aggregates.

Suitability of recycled concrete aggregate for transportation infrastructure embankments and improved subgrade

Transportation Overview - Przeglad Komunikacyjny ◽

10.35117/a_eng_18_11_08 ◽

2018 ◽

Vol 2018 (11) ◽

pp. 72-84

Author(s):

Bartłomiej Krawczyk ◽

Elżbieta Stigler-Szydło

Keyword(s):

Recycled Concrete ◽

Transportation Infrastructure ◽

Concrete Aggregate ◽

Concrete Pavements ◽

Alternative Source ◽

Suitable Material ◽

Crushed Concrete ◽

The paper presents research in the field of utilizing materials recycled from concrete pavements through crushing and re-incorporating them in road embankments and improved subgrade layers. Crushed concrete rubble is an alternative source of aggregates, replacing natural aggregates. Recycled concrete aggregate was tested with regard to the current national requirements. It was proven that recycled concrete aggregate is a suitable material for incorporation into new unbound and cement-bound layers of the improved subgrade. The problem of utilization recycled concrete aggregate in road embankments is also addressed in the paper. Limitations in the use of recycled concrete aggregate are also shown in the paper.

Bricks and Concrete Wastes as Coarse and Fine Aggregates in Sustainable Mortars

Advances in Materials Science and Engineering ◽

10.1155/2018/8676708 ◽

2018 ◽

Vol 2018 ◽

pp. 1-11 ◽

Cited By ~ 8

Author(s):

Alessandra Mobili ◽

Chiara Giosuè ◽

Valeria Corinaldesi ◽

Francesca Tittarelli

Keyword(s):

Crack Formation ◽

Recycled Concrete ◽

Recycled Aggregates ◽

Concrete Aggregate ◽

Capillary Absorption ◽

Coarse Recycled Concrete Aggregate

Environment Friendly ◽

Fine Aggregates ◽

Natural Aggregates ◽

The total substitution by volume of natural coarse calcareous aggregate by coarse recycled brick aggregate (RBA) and coarse recycled concrete aggregate (RCA) has been investigated to produce more sustainable and environment-friendly mortars. Aggregates were also partially substituted by their fines at 12.5% by volume. Mortars have been tested in terms of mechanical, microstructural, and durability properties. Results show that it is feasible to replace a natural calcareous aggregate entirely by recycled aggregates. In particular, the obtained mortars, even if more porous and more prone to the water capillary absorption than that manufactured with natural aggregates, result in less stiffness and thus are less subjected to crack formation, more permeable to water vapour, and less susceptible to sulphate attack.

Toward the use of high volume recycled concrete aggregate in new concrete production

10.32920/ryerson.14664654 ◽

2021 ◽

Author(s):

Anto Sucic

Keyword(s):

High Volume ◽

Recycled Concrete ◽

Mix Design ◽

Concrete Aggregate ◽

Fresh Properties ◽

Waste Concrete ◽

Concrete Production ◽

Hardened Properties ◽

Recycled Material

This thesis reports the findings of a study carried out to determine the feasibility of using Recycled Concrete Aggregate (RCA) in the production of newly made concrete at high replacement levels of conventional coarse Virgin Aggregates (VA). The study evaluated the properties of new concrete produced with coarse RCA, in order to address the issues typically associated with the characteristics of the recycled material. Concrete specimens were tested for fresh properties, hardened properties, as well as overall durability of mixes. Making minor modifications in mix design, the drawbacks typically associated with the use of RCA were successfully mitigated at high replacement levels, making up to a full 100% replacement feasible. Through the use of higher replacement levels of RCA in the production of concrete, the environmental impacts of VA harvesting may be significantly reduced, as well as providing a more economical means of waste concrete disposal for ready mix producers.

VERIFICATION OF THE BASIC PROPERTIES OF RECYCLED AND NATURAL AGGREGATES

Acta Polytechnica CTU Proceedings ◽

10.14311/app.2019.22.0067 ◽

2019 ◽

Vol 22 ◽

pp. 67-71

Author(s):

Karel Mikulica ◽

Iveta Hájková

Keyword(s):

Recycled Concrete ◽

Construction And Demolition Waste ◽

Recycled Aggregates ◽

Concrete Aggregate ◽

Building Structures ◽

Apartment Building ◽

Demolition Waste ◽

Concrete Mixtures ◽

In the future, it is planned to use up to 50% of construction and demolition waste (C&DW) for the production of new building structures. This leads us to think about how we can use recycled concrete aggregate (RCA) as a substitute for natural aggregate (NA) in concrete mixtures. This is why we compare the two typical representatives of recycled aggregates with a representative of natural aggregates. As a representative of recycled aggregates, we chose pure concrete recycled from the cutting of concrete and mixed recyclate from the demolition of the apartment building. As a representative of natural stone, we chose the extracted aggregate.

The use of lithium salts and supplementary cementing materials to control reactivity of recycled concrete aggregate

10.32920/ryerson.14663910 ◽

2021 ◽

Author(s):

Waleed Mikhaiel

Keyword(s):

Preventive Measure ◽

Calcium Content ◽

Recycled Concrete ◽

Alkali Silica Reaction ◽

Alkaline Solutions ◽

Concrete Aggregate ◽

Second Phase ◽

Lithium Nitrate ◽

Supplementary Cementing Materials

This thesis covered the second phase of a study that focused on the reactivity of recycled concrete aggregate (RCA) produced from concrete affected by alkali-silica reaction (ASR). The first phase investigated the reactivity of ASR-affected RCA and the use of Supplementary Cementing Materials (SCM) as a preventive measure. The second phase was carried out to study the efficacy of lithium nitrate, when used individually and in combination with SCM, in suppressing the reactivity of RCA. The use of different dosages of lithium nitrate combined with SCMs reduced expansion due to ASR. However, the expansion results showed that increasing the dosage of lithium beyond a certain level does not help in suppressing the expansion. The high reacitivity of the tested RCA was attiributable to its relatively high alkalis and calcium hydroxide contents that fuel further ASR. The alkalis consumed or contributed from RCA were evaluated through leaching the aggregate particles in distilled water and alkaline solutions at different molarities with and without lithium nitrate. Alkalis consumption was found to decrease when lithium was presented in the leaching solutions. Examining RCA samples under scanning electron microscope (SEM) showed that the crushing process of the RCA exposes fresh surfaces of the reactive virgin aggregate and creates cracks within the particles that provide an easy path of alkalis to reactive sites within the RCA. Examination of the composition of ASR gel showed that exposing the RCA to lithium solution decreased the calcium content and Ca/Si of the gel. This could add to the suggested mechanisms by which the lithium mitigates ASR.